This invention relates to methods and apparatus for forming woodworking joints, especially dovetail and similar joints, and it relates more particularly to devices and techniques for enabling such joints to be cut utilizing a router.
Wooden boxes, drawers and storage chests and a variety of other wooden furniture and other objects often use dovetail joints as a means of securely assembling the sides. Dovetails are used for both their decorative nature and their high strength. Such joints can be made without industrial machinery in one of two principal ways, either using hands tools: saws and chisels, or using power tools such as a router. In both cases, making such ajoint requires a high degree of skill and precision, and in the case of hand tools, time. The desire to save time drives most woodworkers towards the use of power tools, and the need for precision, often in the relative absence of skill, makes jigs or machines that control the power tools desirable.
There are two basic approaches possible when using a router. The router can be held stationary and the workpiece moved relative to the position of the router cutter, or the workpiece can be held stationary and the router moved relative to the workpiece. Additionally, in a variation of both basic approached, both the router and the workpiece can be moved.
This invention is a machine that facilitates cutting of dovetail and other joints such as box joints using an approach in which the position of the rotating router cutter is maintained stationary and the workpiece is moved relative to the cutter. The machine is typically used with a router mounted upside down in a router table so that the router bit or cutter protrudes through a hole in the tabletop. Such a table is disclosed, for instance in U.S. Pat. No. 5,715,880, but this invention is usable with a wide variety of other router tables.
The machine of this invention utilizes an elongated track called a guide that is clamped or otherwise fastened to the router tabletop. Typically, this guide will be positioned so that a router bit or cutter mounted in a router attached to the router table protrudes through the hole in the guide, making it a xe2x80x9ccenter guide.xe2x80x9d A lower fence assembly positions a lower fence transverse to the center guide with base wings attached to the lower fence and contacting either side of the center guide so that the lower fence can slide along the center guide and across the router cutter, which passes through an opening in the lower fence. The opening may be filled with sacrificial material such as wood or ultra high molecular weight (xe2x80x9cUHMWxe2x80x9d) polyethylene. An upper fence that controls the lateral position of a workpiece slides along on the top of the lower fence and can be locked (using a control block and locks associated with it) in position relative to the lower fence.
The position of the upper fence relative to the lower fence can be fixed by reference to predetermined stops positioned by the user in a spacer tray (or, alternatively, the user may make a spacer stick) that is locked in the upper fence. The locations of the stops determines the spacing of joint components and controls movement of the machine components so that joint components are formed in the desired locations on workpieces. In some aspects of operation, such as when pins in through dovetail or finger joints are formed, the upper fence is permitted to slide relative to the lower fence during use of the machine.
Except when making half-blind dovetail tails, the machine functions by clamping a workpiece against one face of the upper fence so that the workpiece stands upright with its end resting against machine wings that in turn rest just above the table top. The lateral position of the upper fence (and therefore the position of the workpiece clamped to it) is determined by interaction among a control block, the upper fence and the lower fence.
The control block can slide along the upper fence or can be locked to prevent such sliding motion. Alternative positions at which the control block is locked to the upper fence are determined by engagement between an indexing pin attached to the control block and holes in spacers positioned in the spacer tray (or holes in a user-made spacer stick), which tray (or stick) is locked into the upper fence during use of the machine. The control block can also be locked to the lower fence so that the relative positions of the upper and lower fences may be secured in a manner limiting or eliminating play between the two fences.
xe2x80x9cTails,xe2x80x9d such as the tails in a dovetail joint, are cut by locking the control block to both the upper fence and the lower fence, which locates the upper fence in selected predetermined positions relative to the lower fence and prevents sliding movement between the two fences, thereby fixing the lateral position of the workpiece relative to the router cutter. The workpiece clamped to the upper fence is then passed around a router cutter having an appropriate shape, such as a dovetail-shaped cutter, by sliding the workpiece and upper and lower fence assembly along the center guide. The cutter exits the workpiece in a space in the lower fence that may be filled with a replaceable block of ultra high molecular weight polyethylene or other sacrificial material. The upper fence is then repositioned to the next predetermined position by unlocking the two fences and moving the upper fence so that the indexing pin can be received in another hole in the spacers in the spacer tray (or in the spacer stick), and a second cut is made. Multiple tail boards or workpieces can be cut simultaneously, limited only by the size of the machine and its capacity to hold workpieces.
xe2x80x9cPins,xe2x80x9d such as pins in a dovetail joint, are cut by mounting on the underside of the control block a template having the shape and, typically, nominal size of each pin to be cut. The control block is locked to the upper fence, but that fence is permitted to move relative to the lower fence, allowing the workpiece to move in two directions: (1) laterally relative to the cutter, and (2) forward along the center guide and into the cutter as described above. The workpiece clamped to the upper fence is then forced into the router cutter while the template is rubbed against a tracer pin located in a tracer pin jack secured to the center guide, for instance, by screwing a threaded pin jack base into a threaded hole in the center guide. Contact between the tracer pin and template allows material to be cut away from the workpiece except where the workpiece pin is desired. After formation of a pin in one desired location on the workpiece by removing the adjacent waste, the control block is repositioned on the upper fence by moving the indexing pin to another hole in the spacer tray, and the operation is repeated to form another pin at another desired location. Since lateral positioning of the upper fence is controlled in each instance by the spacer in the same spacer tray (or hole in a spacer stick), joint pins and tails are formed in the same locations.
The tracer pins have a conical shape and are used in multiple sizes to make possible a wide range of joint component sizes. The height of each tracer pin relative to the router tabletop and the template is adjustable using the pin jack. This makes possible adjustments in the size of joint pins produced using a particular template, because changes in tracer pin height change the effective diameter of the tracer pin in contact with the template.
Joint tails in half-blind dovetail joints are cut with the tail-containing workpiece face down on the wings that lie just above the router table top. The lower fence is fixed in place on the router tabletop, or a stop is utilized to fix lower fence travel along the center guide, to thereby limit the distance the dovetail cutter enters the workpiece as the workpiece travels against the cutter. An auxiliary fence is secured to the upper fence projecting at a right angle from the upper fence (parallel to the center guide). With the upper fence positioned relative to the lower fence with the indexing pin in one of the spacer holes as described above, the workpiece is slid along the auxiliary fence and into the dovetail cutter and then back out. Alternatively, if the lower fence is permitted to move until it reaches a stop, the workpiece is positioned against the auxiliary and lower fences, and the workpiece and fences are slid so that the cutter enters the workpiece until the stop is reached. The upper fence is then relocated by moving the indexing pin to another spacer hole, and the workpiece is again slid along the auxiliary fence and into the dovetail cutter, or the workpiece and fences are slid as described above, to make a second and subsequent cuts.
The track or guide and fence components can be made of extruded aluminum, and most of the other components can be made of a variety of metals, including steel, brass, and aluminum as well as other materials, including plastics and other materials.
The machine and techniques of this invention facilitate cutting the most common joints, through dovetail, half-blind dovetail and finger joints. The machine can also cut rounded finger joints, double-sided rounded finger joints, double sided dovetails and rounded dovetails. FIG. 21 illustrates some of these joints. With appropriately shaped cutters and templates other joint shapes are also possible. Because it is necessary to have only one template for a particular joint shape, it is practical for the user of the joint-making machine of this invention to make templates and create joints in any desired shape within the broad range of shapes possible. It also makes it economical for a user to purchase alternative templates because only one is need for any desired new shape (within certain size limits for that shape).
This invention therefore provides a versatile joint making machine for use with a router to make woodworking joints. This invention is accurate, easy to use, and easy to set up for making a wide range and variety of different joints with user selected spacings of joint elements. Other advantages and benefits of this invention will be apparent to those skilled in the art from the drawings and the following description of the invention and claims. For instance, the capabilities of this invention can be used not only for creating joints but for creating repeating patterns in items such as moldings, an operation that may be facilitated by use of an apparatus controlling vertical positioning of the router bit so that it can be lifted through the router table into the workpiece when desired. Such a device for controlling the vertical position of the router bit is disclosed in U.S. Pat. No. 5,918,652, which is incorporated herein by reference.